P.W.E. New Kowloon
110
It was found economical to extend the 'open cut' section at the North end for a distance of about 140 ft. further than was originally intended.
This resulted in reducing the length actually tunnelled to 2,020 ft. The portable compressor engaged on the open cut work also drove from the north end the 149 ft. of Tunnel referred to above, the remaining distance of 1,871 ft. having been driven from the central depot between the North and South Tunnels.
The rock throughout this Tunnel was found to be generally of a poor quality, numerous patches of shale, soft clay and in two cases running sand and clay were encountered.
Altogether eleven separate lengths of lining were required having a total length of 362 ft.
Some difficulty was experienced in depositing the lining owing to seepage from the soft patches already referred to.
The lining is of 6 to 1 cement concrete of minimum thickness of 6" and 12", but in one length traversing a seam of loose clay and running sand cement concrete packing was put in to a height of 20 ft. above the normal level of the Tunnel roof.
The minimum Tunnel dimensions are as follows:-
Width at invert - 7′0′′
Width 4 ft. above invert - 9′0′′
Total height - 7'6"
The roof is arched to a radius of 4.65 ft. and the invert is dished to a radius of 12.50 ft.
The tunnel has a total fall of 9" or 1 in 2,700, and the invert has been graded smooth with a layer of cement concrete of a minimum thickness of 3".
South Conduit. This Conduit has a total length of 2,000 ft. and has been constructed of 8 to 1 cement concrete throughout.
Its inside dimensions are as follows:—
Width at invert - 3′6′′
Width at overflow level - 6′6′′
Height of overflow above invert - 4′0′′
Height of path level above overflow level - 6′′
A 2 span reinforced concrete bridge carrying the Conduit and footpath was constructed across the stream from Smugglers Pass. More work than was anticipated was found necessary owing to the mass of loose boulders comprising the stream bed.